Communication terminals, such as aerial communication devices that operate at high altitudes, may transmit and receive optical signals through free space optical links. Free-space optical communication systems are an attractive solution for meeting increasing bandwidth demands. Density of the air, wind speeds, air pressure, and turbulence may cause air scintillation across optical links to fluctuate. Air scintillation may result in optical power fades over optical signals communicated between the communication terminals. There is no correctable action when optical power fades become too deep, thereby rendering optical communication links between communication terminals unavailable.
Fading mitigation techniques are employed by free-space optical communication systems in order to keep the optical link available when optical power fades are present. For example, spatial and time/wavelength diversity schemes send replicas of data to increase the probability that one of the replicas of the data will propagate through a less turbulent medium that avoids the optical power fade. In spatial diversity, two wavelengths carrying the same data are transmitted from two different physical locations. However, spatial diversity requires redundant physical hardware for the two locations, adding additional space, weight, and power requirements. In time/wavelength diversity, two wavelengths carrying the same data are transmitted from the same physical location, but delayed in time. While only one physical location is required for time/wavelength diversity, the use of an additional optical channel requires twice as much transmit optical power to achieve the same capacity as a single optical channel.